The present invention relates to a lead-free balance weight, which is used for controlling weight balance of a vehicle wheel in automobiles and motorcycles.
In case where well weight balance (wheel balance) of a vehicle wheel in automobiles and motorcycles is not attained, abnormal vibration of the wheel is caused by high-speed rotation of tires on running of the vehicle. This vibration is transferred to a steering to impair the comfortability on driving, or exerts an adverse influence on performances of automobiles as a result of the occurrence of an abnormal abrasion of tires. Accordingly, it is very important to control the wheel balance.
A method of mounting and fixing a balance weight to a light point of the wheel balance is employed to attain well wheel balance. The balance weight is requested to have enough small size to cause no impairment of the appearance of the wheel and to have enough flexibility to deform easily corresponding to the rim diameter of the wheel and the shape of a flange.
Therefore, there has widely been used a balance weight made of lead, which can realize size reduction because of its high specific gravity, and has proper flexibility.
However, it is notorious that lead has toxicity to the human body. Therefore, it has been a problem to use lead from an environmental point of view.
On the other hand, it has been suggested to use a balance weight made of iron in place of the balance weight made of lead. However, the balance weight made of iron had such a drawback that the volume becomes larger by about 1.44 times to obtain a balance weight having the same weight because the specific gravity (7.86) of iron is considerably smaller than the specific gravity (11.35) of lead.
The balance weight made of lead can be easily deformed, but it is very difficult to appropriately change the shape of the balance weight made of iron on attachment because iron is very hard. Accordingly, there arises a problem that the balance weight can not be firmly fixed to the wheel.
Recently, a wheel made of aluminum has frequently been used. However, the wheel made of aluminum itself is liable to be scratched by the balance wheel made of iron when some impact is applied to the wheel because the hardness of iron is higher than that of aluminum.
An object of the present invention is to provide a balance weight for vehicle wheel, which can be securely fixed to the wheel without using lead.
The present inventors have intensively studied to solve the above problems and found out such a novel fact that a balance weight having high specific gravity and proper flexibility can be obtained when using:
(1) as a clip 14 a metal member (see FIGS. 1 and 2) comprising:
a hook portion 11 formed corresponding to the shape of a flange edge portion 34 of a wheel, particularly the thickness of the flange edge portion 34, the hook portion serving as a hook for hanging on the flange edge portion, and
a leg portion 13 capable of retaining a weight used for controlling the weight of the balance weight, easily and securely, wherein the shape is controlled to enable the clip to be close-contacted independently and fixed firmly to the flange edge portion 34 and a distance 11a of the of the hook portion is formed corresponding to the thickness of the flange edge portion 34; and when providing:
(2) the leg portion 13 of the clip 14 with a weight 12 made of a thermoplastic resin (see FIGS. 1 and 2) containing a predetermined amount of tungsten powder, in a balance weight comprising a metal clip and a weight attached to the clip. Thus, the present invention has been completed.
That is, the balance weight for vehicle wheel according to the present invention comprises:
a metal clip comprising a hook portion having a cross-sectional shape corresponding to a flange edge portion of a wheel, and a leg portion for retaining a weight, which is capable of independently close-contacting and fixing to the flange edge portion, and
a weight made of a thermoplastic resin comprising 2.5 to 8.0% by weight of a thermoplastic elastomer and 97.5 to 92% by weight of tungsten powder, which is attached to the leg portion of the metal clip.
According to the balance weight for vehicle wheel according to the present invention, there can be obtained the following merits:
(a) There is no fear of burden to the environment such as human body because lead having toxicity to the human body is not used (lead-free);
(b) Since a leg portion of a metal clip is provided with a weight made of a resin composition having very high specific gravity equivalent to that of lead, specifically 11.5 g/cm3, the total weight can be increased while maintaining the size of a balance weight;
(c) A weight portion can be molded by injection molding because the material thereof is a thermoplastic resin composition and, moreover, the moldability is good and the weight portion can be reused;
(d) Since a weight portion is made of the resin composition in place of lead, the flange of the wheel is not scratched when the balance weight is assembled (mounted) to a steel wheel or an aluminum wheel;
(e) The weight portion can be easily cut because it is made of the resin composition so that fine control of the weight can be easily realized;
(f) Sufficient durability can be obtained in general use, as is apparent from the Examples described below, though the weight portion is made of the resin composition;
(g) Since the balance weight is a clip type one similar to a conventional balance weight, it is easily assembled or removes off and is superior in handling; and
(h) The metal clip can be independently close-contacted to the flange edge portion (without interposing the resin thereby making it possible to firmly fix to the wheel (improvement in retention) and, furthermore, the balance weight can be securely fixed and deviation can be sufficiently prevented, thereby making it possible to retain well balance of the vehicle tire for a long period.